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Mobile Compressors

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Most of the compressors that we will talk about are stationary compressors. However there are also mobile compressors. These are used for a great amount of applications, ranging from construction and road repair to salvaging operations. Almost all of them are diesel powered compressors.

What are mobile compressors and what are they used for?

As mentioned earlier, nearly all mobile compressors are diesel engine powered oil-injectedscrew compressors. Very small as well as very large mobile compressors are sometimes offered with electric motors. Oil-free mobile compressors are produced only by the world's leading manufacturers, for service work in the process industry, utilities and offshore industry. Whereas mobile compressors initially were used on construction sites and for off-road drilling, they are now being used in many more applications and processes: road repair, pipeline work, rock reinforcement, sandblasting, salvaging operations, etc. Generally, mobile compressors are packaged as standalone compressed air plants with optional, integrated air treatment equipment on-board (aftercooler, water separator, fine filters, reheater, lubricator, etc.) as well as optional auxiliary equipment (5 to 10 KVA electric power generator 230V/400V, cold start aids, anti-theft devices, spillage-free chassis etc). There are mobile, diesel powered electric power generators built in similar enclosures as mobile compressors for larger power requirements.

Noise level and exhaust emissions

Modern designs of diesel-powered compressors provide very low noise levels as a result of widespread legislation including the EU Directive 2000/14/EC governing noise emissions from machinery used outdoors. These machines can therefore be used without negatively impacting populated areas and areas near hospitals, etc. The silencing enclosure is generally a single-wall steel construction, although double-wall steel and even durable polyethylene enclosures have recently been introduced, containing special baffling and substantial amounts of sound absorbing foam.

Over the past two decades, fuel economy has improved substantially by introducing very efficient screw compressor elements and efficient packaging. This has been especially valuable for water well drilling, which is a task that requires the compressor to work intensively over a long period of time. Moreover, modern compressors can be equipped with fuel economy optimizing hardware and software that is far superior to the conventional pneumatic engine/compressor control systems, for example FuelXpert and DrillAirXpert.

Since the introduction of specific exhaust emission legislation in 1997 in the United States, Europe and elsewhere, diesel engines that comply with latest exhaust gas emission requirements are being chosen more often: EURO III will be introduced between 2006-2013, EURO IV from 2014 on, and US Tier 4 between 2008 and 2015.

Operational flexibility of mobile compressors

Whereas stationary industrial compressors are installed to serve only one or a few applications along a common compressed air distribution system, modern mobile compressors must demonstrate high overall operational flexibility to serve a multitude of applications in different environments based on ambient temperatures, humidity levels, working pressures, altitudes and load cycle profiles. Other requirements relative to mobile compressors include high operating reliability, good service characteristics, small environmental impact resulting from low noise levels and regulated exhaust emission levels, compact dimensions and a low total weight.

Operation in climates with medium to high humidity, in particular when the load/unload profile contains load cycles at high pressure or long periods of unload operation, will cause some of the atmosphere water content to condense inside the compressor oil circuit. This has a negative impact on the lubricated compressor components as well as on the oil itself. Having just 1% of water in the oil will reduce the useful life of the bearings by 40%. The most modern mobile compressors can be equipped with an electronic oil temperature control system to protect the compressor's operating life.

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